philosophical one; that is, it must be comparatively correct to coincide with the scale in such a manner, that every urine of any given colour of the scale, by dilution with its equal amount of water, may produce the next following dilution, and that the darkest urine, on being diluted the necessary number of times, will produce all the colours of the scale in succession; in other words, that the gradations of the unit are simple multiplications by two.

The unit, then, is the amount of uræmatine, or colouring matter, contained in 1000 c.c. of the first variety, or paleyellowish urine. This amount, no matter to how much it may amount in real weight, is put down as = 1. 1000 c.c. of yellow urine (III) therefore contain four times as much uræmatine as 1000 c.c. of the first variety; and 1000 c.c. of yellow urine will require three times their own bulk of water for becoming of the pale-yellow colour of variety 1. The following table is intended to represent these relations more perspicuously:

This table shows how much uræmatine is contained in equal parts of urine of different colours. To illustrate it with another example; if a certain volume of pale-yellow urine contains 1 part of uræmatine, the same volume of reddishyellow urine contains 8 parts, and the same volume of reddish-brown urine 128 parts of uræmatine. One volume of yellow urine, on the other hand, contains just as much colouring matter as 4 volumes of pale yellow; 1 volume of red urine the same quantity as 4 volumes of reddish-yellow urine. If, therefore, an individual discharge 1000 c.c. urine of yellow colour in twenty-four hours, and another, during the same period of time, 4000 c.c. of pale-yellow urine, both discharge equal quantities of uræmatine during the same time. And if an individual discharge any number of c.c. of urine of a certain colour during a given time, the amount of colour

ing matter thereby discharged is ascertained by simple equation. For example, in twenty-four hours there were discharged 1800 c.c. of urine of yellow colour; 1000 c.c. contain 4 parts, how much do 1800 contain?

1000 : 4 = 1800 : x

=

x = 7.2 the amount of uræmatine contained in 1800 c.c. of yellow urine.

In order to obtain uniform results by this method, it is essential that the urine be absolutely clear. It has, therefore, to be filtered in most instances. Its colour must be ascertained by transmitted light, and for this purpose the body of urine should be of a diameter of not less than four or five inches.

Several objections have been raised against this method, which have been answered satisfactorily by its originator. It is quite clear that in cases where the colour of the urine depends on any other substance than uræmatine, it would give erroneous results. But these cases can, in the first instance, easily be detected by the tests given when treating of the colour of urine; and, in the second instance, they are of rare occurrence as compared with the great number of instances in which the urine is coloured by the ordinary uræmatine only.

In some rare cases the urine on dilution will not yield the colours which would correspond to the scale. In these cases it may be doubtful whether a red urine contains 32 times, or a brownish-red urine 64 times the amount of uræmatine contained in the same quantity of pale-yellow urine. It may well be admitted that modifications of the uræmatine occur, which have a different colouring power from that of the ordinary substance. Admitting all this, we may still coincide with Vogel in the opinion that, for approximative determinations of the quantity of uræematine discharged in a given time, the method is useful. An error is not so dangerous, if we know the extent to which it can be committed, and the sources from which it may arise. Of the sources we have spoken; we can say less of the extent, as we do not know to what quantity of uramatine a certain colour corresponds. The highest amount of error to which, in the opinion of Vogel, his method might be liable, is one third or one fourth of the figures found. Fluctuations, therefore, within these limits might be left out of the question; but when they surmount certain boundaries, they may with safety be used for the comparison of the quantity of uræmatine contained in two different descriptions of urine. Thus, if the quantity

of uramatine which is discharged in the urine by a healthy individual in twenty-four hours amounts to 4, and we find that in the urine of a patient, for twenty-four hours, it amounts to 16 or 20, there can be no doubt that the quantity of uræmatine discharged by the latter is double or three times the amount of that discharged in the same time by the healthy individual. If, on the other hand, we find in the urine of a patient the amount of uræmatine to be 1 for twenty-four hours, its quantity is clearly diminished. If, however, we find 35, or 4-5, as the amount of uræmatine in the urine of a sick person, we could not say with certainty whether the amount of uræmatine was diminished or increased in this case.

Physiology of Uramatine.

It is very probable that a number of blood-corpuscles are constantly undergoing the process of disintegration in the blood, and that the hæmatine which is thus set free, however changed from its original character, finds its way out of the body in the form of colouring matter of bile (cholæmatine) and uræmatine. We know the indestructible nature of hæmatine, how obstinately it retains its colour under the most varied circumstances, whether in extravasations within the body, or during artificial or natural processes of decomposition out of the body. We know, moreover, that the changes of colour which hæmatine undergoes under certain circumstances in the body-for example, when effused into a bruise under the skin or epidermis-correspond with the destructive changes in the blood; so that hæmatine thus effused will go through all the stages of colour from red to green, yellow, and pale yellowthe colours which are found in the cholæmatine and uræmatine. From this property of retaining its colour under the most varied circumstances, it is highly improbable that hæmatine, after having served the economy, should leave the body as a colourless substance. And if it, therefore, is probable that effete hæmatine is discharged as a coloured substance, the only excreta which are coloured, namely, fæces and urine, most probably owe their colour to effete hæmatine. If we, moreover, take into consideration that the purest uræmatine always contains some iron in chemical combination, it can scarcely be doubted that it is the offspring of the colouring matter of the blood-corpuscles.

The quantity of uramatine which, according to Vogel, is discharged by an adult healthy person in twenty-four hours,

amounts to from 3 to 6 of the above units, and, on an average, to about 48, which, calculated upon the hour, gives 0.2.

Quantity of Uraæmatine in Disease.-Pathological Indications.

According to the observations of Professor Vogel, which may be verified by daily observation at the bedside, the amount of uræmatine discharged during acute febrile diseases is considerably increased, and, notwithstanding a considerable decrease in the total quantity of urine, amounts to 16, 20, and more. This amount becomes even much higher in typhoid and septical fevers, which are combined with dissolution of the blood. In accordance with this we observe, that in the course of all these diseases the amount of blood-corpuscles in the blood becomes so considerably diminished as to cause an anæmic, or better oligocythæmic, condition. In a number of pneumonic patients the daily amount of uræmatine fluctuated during the acme of the disease between 16 and 24. During the acme of a case of acute rheumatism it was 30 to 32. In a case of typhus in a man it was for some days 80 to 100. In a case of lead colic I found it 64 for three days. In a case of scarlatinous nephritis I found it on two occasions 256 for twenty-four hours.

In cases where the disintegration of the blood-corpuscles is diminished, as in chlorosis and anæmia, in hysterical and nervous diseases, and in the convalescence from severe diseases, the quantity of uræmatine discharged during a given time is generally diminished. In these cases the condition of the urine affords valuable therapeutic indications, as pointing to the exhibition of tonics, in particular iron.

In chlorotic patients the daily quantity of uræmatine is frequently below 1; in the convalescence from severe diseases it is frequently, for some length of time, not above 1 or 2 (Vogel). In a case of ovarian tumour I found it below 1 (vide p. 75). This urine resembles that of young children who are growing fast, but has of course a different signifi

cance.

From this composition the following formula is derived: C1H.NO, +HỎ, or C1H,NO.

History and Literature.

Rouelle (1781), Fourcroy and Vauquelin (1799) 'Journ. d. Pharm.,' von S. B. Trommsdorff, v, p. 197; vii, p. 199, found it in the urine of graminivorous animals, but mistook it for benzoic acid.

Scheele, Fourcroy, and Reynard demonstrated its existence in the urine of young infants.

Proust, Ann. de Chim. et de Phys.,' xiv, 260 (1820), found it as benzoic acid in the distillate from putrid urine. Liebig, 'Poggend. Ann.,' xvii, p. 389 (1830), demonstrated hippuric acid to be a peculiar substance, distinct from benzoic acid, with which it had been confounded.

Ure, Med.-Chir. Transact.,' vol. xxiv, and Keller, Ann. d. Chem. und Pharm.,' xliii, p. 198, proved that benzoic acid is transformed in the body into hippuric acid.

Liebig, Ann. d. Chem. und Pharm.,' 1, p. 161, proved its existence as a normal ingredient in the urine of man.

Dessaignes, Compt. rend.,' xxi, p. 1224, found that glycocoll combines with benzoic acid to form hippuric acid.

In the course of his researches on putrefied urine, Proust made the observation that during the distillation of such